Experimental research on the thermal hydraulic characteristics of liquid sodium flowing in annuli with low Peclet number

Thermal hydraulic characteristics of liquid sodium flowing in annuli with low Peclet number are experimentally studied. Two test sections are used: the inner and outer diameters are 6 mm and 10 mm, respectively for test section No. 1, and 8 mm and 12 mm for test No. 2. Both the two annuli are 1100 mm long. In the experiment, the heat flux ranges from 50 to 210 kW/m², Reynolds (Re) number from 0 to 18,000 and average fluid temperature from 200 to 500 °C. Experimental data show that the flow regime of liquid sodium flowing in annuli can be divided into three regions, i.e. laminar flow (Re < 2000), transition flow (2000 < Re < 4000) and turbulent flow (Re > 4000). The effects of heat flux, Re number and average fluid temperature on the heat transfer coefficients are investigated separately. Correlations for the friction coefficient and for the Nusselt (Nu) number are obtained based on the experimental data in the three flow regions.